The invention is related to hydrometallurgical processes for the recovery of copper from its ores, particularly, sulfide ores, in which the ore concentrate is leached with ferric chloride and/or cupric chloride to solubilize the copper as the chloride and produce elemental sulfur. This type process is illustrated by those described in U.S. Pat. Nos. 3,785,944; 3,798,026; 3,879,272; 3,972,711; 4,013,457; 4,039,324. The disclosure of some of these patents includes chemical equations illustrating the reactions occurring when chalcopyrite is leached with ferric chloride and cupric chloride to solubilize the copper and produce elemental sulfur. Some of the patents further describe how copper is recovered from the formed cuprous chloride by crystallization followed by recovery of copper from the crystallized cuprous chloride. The prior art discloses various other methods for the recovery of copper from the leach solution resulting from the leaching of copper ores and concentrates with ferric chloride and/or cupric chloride.
Copper sulfide ores, in particular, contain materials which are insoluble in ferric chloride and cupric chloride leachants and are usually discarded in the tails from hydrometallurgical leaching with these leachants. These materials may include valuable substances, such as, the elemental sulfur formed in the leaching reactions as well as gold and molybdenum values. They also may contain impurity-like materials, such as, pyrite, jarosite and others. If the pyrite contains gold it is not rejected in the flotation step. Some of the copper sulfide mineral which is embedded in the mineral grains is not dissolved by the leachant as the leachant does not come into direct contact with the copper mineral and this undissolved mineral is contained in the tailings.
As the processes for recovery of copper from its sulfide ores which are acceptable under environmental regulations are quite competitive, it is important from an economic standpoint to have available effective procedures which are compatible with the copper recovery processes for recovering saleable elemental sulfur and metal values from the tailings. Such a process should be one that is adaptable to pilot plant production in a continuous operation and no such process is known to be available today. A major difficulty has been that the relatively small amounts of metal values in the ore other than copper have been contained in large bulk volumes of gangue after concentrating the copper ore and it was not possible to economically process this large bulk of material to recover the relatively small amounts of metal values. This was particularly true in prior processes in which sulfur was removed from the ore by pyrometallurgical processes. Difficulty has been encountered in separating elemental sulfur in the presence of copper and molybdenum in the concentrates. A further difficulty has been encounted in recovering molybdenum in the presence of copper which is not contaminated by the copper to the point where the molybdenum is unsaleable, and at the same time achieve high recovery of molybdenum. Any molybdenum left in the tails ordinarily could not be recovered. If gold is present it will also contaminate the molybdenum.
Accordingly it is the object of this invention to provide a process for the recovery from tailings resulting from the hydrometallurgical processing of copper ores, of elemental sulfur, copper, gold and molybdenum in one continuous operation in which the tailings from which the sulfur and metal values are recovered are first reduced to a relatively small bulk volume.
It is another object of this invention to provide a process for the recovery of a higher percentage of the copper from the tailings resulting from the hydrometallurgical processing of copper sulfide ores.
It is a further object of this invention to provide a process for the recovery from tailings from the hydrometallurgical processing of copper sulfide ores, of molybdenum which is not contaminated with copper, or gold, if present, to the extent that the molybdenum does not meet the purity standards for a saleable product.